Elucidating the Structure of pH-Responsive PAMAM Dendrimer Aqueous Solutions: A Combined Experimental/Modeling and Simulation Approach

Bamin Khomami (University of Tennessee, USA), Hanieh Niroomand (University of Tennessee, USA), and Wei-Ren Chen (Neutron Scattering Science Division, Oak Ridge National Laboratory, USA)

Polyamidoamine dendrimers (PAMAM) with ethylenediamine (EDA) cores and amino groups are synthetic, nanoscale macromolecules with tremendous potential in gene and drug delivery applications. While to date a number of studies have focused their attention on elucidating the single molecular conformation of PAMAM dendrimers in dilute solutions, much less is known about the structure and dynamics of PAMAM macromolecules in concentrated solutions. Considering the fact that biomedical applications of PAMAM dendrimers will require concentrated solutions, understanding the structure and dynamics of this class of solutions is of significant scientific and industrial importance. To this end, a highly synergetic experimental and multi-scale modeling and simulation approach is being undertaken. The specific objectives of the research program are:

  1. To perform an experimental investigation of charged PAMAM dendrimers aqueous solutions via small-angle neutron scattering (SANS) and model development for conversion of the measured scattering intensity into dendrimer and solution nano-structure;
  2. To establishing the relationship between dendrimer volume fraction, pH and charge, and the solution nanostructure via shear viscosity measurements;
  3. Determination of the structure factors of PAMAM dendrimer aqueous solution via Monte Carlo (MC) simulations.

It is anticipated that through this highly synergetic collaboration, we will be able to develop a fundamental understanding of general soft colloidal interactions as well as establishing the foundation for rational design of an effective dendrimer-based drug-delivery system.